Implement a CDS Hooks appointment-book service that checks prior authorization requirements and formulary coverage before an appointment is confirmed and returns actionable cards

Verified steps

1. Register the hook service in your discovery endpoint at /.well-known/cds-services returning a services array entry with hook set to appointment-book, and define a prefetch template that requests the draft Appointment resource and the patient's active Coverage resources
2. In the hook handler, extract the Appointment resource from the context object using the appointments key, identify the service type code and performing provider from the Appointment, and use the patient's Coverage to determine the applicable payer and plan
3. Query the payer's prior authorization requirements by calling the Da Vinci CRD endpoint or a payer formulary API using the coverage member ID extracted from the prefetched Coverage resource, passing the procedure or service type code from the Appointment
4. If prior authorization is required, return a CDS Hooks card with indicator warning, a human-readable summary message, and a suggestion object that carries a create action adding a Task resource to the patient chart flagging the prior authorization need
5. If the service involves a medication with formulary implications, return a separate card with a SMART app link action pointing to a formulary check SMART app, passing the appointment context in the appContext parameter so the app can pre-populate the drug lookup
6. Include a source object in every card with a label and url pointing to the payer's coverage policy or formulary, so the clinician can review the underlying policy before taking action